Catheters are increasingly used to access remote regions of the human body and, in doing so, delivering diagnostic or therapeutic agents to those sites. In particular, catheters which use the circulatory system as the pathway to these treatment sites are especially useful. For instance, it is commonplace to treat diseases of the circulatory system via angioplasty (PCTA) using catheters having balloons on their distal tips. It is similarly common that those catheters are used to deliver a radiopaque agent to that site prior to the PCTA procedure to view the problem prior to treatment.
Often the target which one desires to access by catheter is within a soft tissue such as the liver or the brain. The difficulty in reaching such a site must be apparent even to the casual observer. The catheter must be introduced through a large artery such as those found in the groin or the neck and be passed through ever more narrow regions of the arterial system until the catheter reaches a selected site. Often such pathways will wind back upon themselves in a multi-looped path. These catheters are fairly difficult to design and utilize in that they must be fairly stiff at their proximal end so to allow the pushing and manipulation of the catheter as it progresses through the body, and yet must be sufficiently flexible at the distal end to allow passage of the catheter tip through the loops and increasingly smaller blood vessels mentioned above and yet at the same time not cause significant trauma to the blood vessel or to the surrounding tissue. Further details on the problems and an early, but yet effective, way of designing a catheter for such a traversal may be found in U.S. Pat. No. 4,739,768, to Engelson. These catheters are designed to be used with a guidewire. A guidewire is simply a wire, typically of very sophisticated design, which is the "scout" for the catheter. The catheter fits over and slides along the guidewire as it passes through the vasculature. Said another way, the guidewire is used to select the proper path through the vasculature with the urging of the attending physician and the catheter slides along behind once the proper path is established.
There are other ways of causing a catheter to proceed through the human vasculature to a selected site, but a guidewire-aided catheter is considered to be both quite quick and somewhat more accurate than the other procedures. One such alternative procedure is the use of a flow-directed catheter. These devices often have a small balloon situated on the distal end of the catheter which may be alternatively deflated and inflated as the need to select a route for the catheter is encountered.
This invention is an adaptable one and may be used in a variety of catheter formats. The invention utilizes the concept of combining a polymeric tubing with one or one or more spirally wound ribbons to control the stiffness of the resultant catheter body. This catheter may be used in conjunction with a guidewire, but the catheter body may also be used as a flow-directed catheter with the attachment of a balloon or in combination with a specifically flexible tip, as is seen, for instance, in U.S. application Ser. No. 08/023,805 to Zenzen et al., the entirety of which is incorporated by reference.
The use of ribbons in winding a catheter body is not a novel concept. However, none have used this concept to produce a catheter which has the physical capabilities of the catheter of this invention.
Examples of previously disclosed catheters include U.S. Pat. No. 2,437,542, to Crippendorf. Crippendorf describes a "catheter-type instrument" which is typically used as a ureteral or urethral catheter. The physical design is said to be one having a distal section of greater flexibility and a proximal section of lesser flexibility. The device is made of intertwined threads of silk, cotton, or some synthetic fiber. It is made by impregnating a fabric-based tube with a stiffening medium which renders the tube stiff yet flexible. The thus-plasticized tubing is then dipped in some other medium to allow the formation of a flexible varnish of material such as a tung oil base or a phenolic resin and a suitable plasticizer. There is no indication that this device is of the flexibility required herein. Additionally, it appears to be the type which is used in some region other than in the periphery or in soft tissues of the body.
Similarly, U.S. Pat. No. 3,416,531, to Edwards, shows a catheter having braiding-edge walls. The device further has layers of other polymers such as TEFLON and the like. The strands found in the braiding in the walls appear to be threads having classic circular cross-sections. There is no suggestion of constructing a device using ribbon materials. Furthermore, the device is shown to be fairly stiff in that it is designed so that it may be bent using a fairly large handle at its proximal end. There is no suggestion to either merely wind ribbon onto a polymeric substrate to form a catheter or, in particular, to make one of such flexibility as is required herein.
U.S. Pat. No. 4,484,586 shows a method for the production of a hollow, conductive medical tubing. The conductive wires are placed in the walls of hollow tubing specifically for implantation in the human body, particularly for pacemaker leads. The tubing is made of, preferably, an annealed copper wire which has been coated with a body-coompatible polymer such as a polyurethane or a silicone. The copper wire is coated and then used in a device which winds the wire into a tube. The wound substrate is then coated with another polymer to produce a tubing having spiral conducting wires in its wall.
A document showing the use of a helically wound ribbon of flexible material in a catheter is U.S. Pat. No. 4,516,972, to Samson. This device is a guiding catheter and it may be produced from one or more wound ribbons. The preferred ribbon is an aramid material known as Kevlar 49. Again, this device is a device which must be fairly stiff. It is a device which is designed to take a "set" and remain in a particular configuration as another catheter is passed through it. It must be soft enough so as not to cause substantial trauma, but it is certainly not for use as a guidewire. It would not meet the flexibility criteria required of the inventive catheter described herein.
U.S. Pat. No. 4,806,182, to Rydell et al., shows a device using stainless steel braid imbedded in its wall and an inner layer of polyfluorocarbon. The process also described therein is a way to laminate the polyfluorocarbon to a polyurethane inner liner so as prevent delamination.
U.S. Pat. No. 4,832,681, to Lenck, shows a method and apparatus for artificial fertilization. The device itself is a long portion of tubing which, depending upon its specific materials of construction, may be made somewhat stiffer by the addition of spiral reinforcement comprising stainless steel wire.
Another catheter showing the use of braided wire is shown in U.S. Pat. No. 5,037,404, to Gold et al. Mention is made in Gold et al of the concept of varying the pitch angle between wound strands so to result in a device having differing flexibilities at differing portions of the device. The differing flexibilities are caused by the difference in pitch angle. No mention is made of the use of ribbon, nor is any specific mention made of the particular uses to which the Gold et al. device may be placed.
U.S. Pat. No. 5,069,674 shows a small diameter epidural catheter which is flexible and kink-resistant when flexed. The wall has a composite structure including a helical coil, typically stainless steel or the like, a tubular sheath typically of a polymer, and a safety wire which is spiraled about the coil and is often in the shape of a ribbon.
U.S. Pat. No. 5,176,660 shows the production of catheters having reinforcing strands in their sheath wall. The metallic strands are wound throughout the tubular sheath in a helical crossing pattern so to produce a substantially stronger sheath. The reinforcing filaments are used to increase the longitudinal stiffness of the catheter for good "pushability". The device appears to be quite strong and is wound at a tension of about 250,000 lb./in..sup.2 or more. The flat strands themselves are said to have a width of between 0.006 and 0.020 inches and a thickness of 0.0015 and 0.004 inches. There is no suggestion to use these concepts in devices having the flexibility and other configurations described below.
U.S. Pat. No. 5,178,158, to de Toledo, shows a device which is a convertible wire having use either as a guidewire or as a catheter. The coil appears to be a ribbon which forms an internal passage through the coil/catheter device. No interior coating is applied.
U.S. Pat. No. 5,217,482 shows a balloon catheter having a stainless steel hypotube catheter shaft and a distal balloon. Certain sections of the device shown in the patent use a spiral ribbon of stainless steel secured to the outer sleeve by a suitable adhesive to act as a transition section from a section of very high stiffness to a section of comparatively low stiffness.
None of these devices are catheters which have the critical bend diameter required herein, nor do they have the compression strength, or flexibility of the present invention.